1. Field of the Invention
The present invention relates to the use of a sealable film for the production of tear-open packaging.
2. The Prior Art
Conventional blown films or flat films have very different mechanical properties in the lengthwise and the crosswise direction. While films made of polypropylene preferably tear in the machine running direction, tears in polystyrene films preferably propagate themselves crosswise to the machine running direction. The anisotropic mechanical properties are a disadvantage when these films are used as film packaging. When a film package is opened, there is the particular problem that the film package tears open in an uncontrolled manner.
Furthermore, cycloolefin copolymers are known as film materials (Verpackungs-Rundschau 9/18, pages 52 to 54). The raw material basis for cycloolefin copolymers is ethylene and dicyclopentadiene, from which the comonomer norbornene is obtained. Cycloolefin copolymers, abbreviated as COC, are produced from norbornene by solvent polymerization with ethylene, using metallocene catalysts. Cycloolefin copolymers are amorphous, relatively rigid and brittle, highly transparent plastics, the glass transition temperature of which can be modified by means of the installation ratio of ethylene and norbornene. Because of the brittle character of the polymers, the films possess a low tendency to tear and tend to break if they are bent severely. The mechanical properties of these materials can be modified by mixing them with polyolefins.
Deep-drawable laminate films, which have a layer of cycloolefin copolymer and at least one layer made from a polyolefin, are known from EP 1 213 138 A1. The connection between the COC layer and the polyolefin layer is produced by means of an adhesion agent, e.g. on the basis of a linear polyethylene.